Clicking behind driver seat - sounds like someone is doing morse code

[03 raw nsx]

Hey Guys,

I have a clicking sound like a relay opening and closing quickly behind the left seat. It sounds like some is tapping Morse code. Car drives fine and there isn't any CEL's. I haven't pulled the panel cover to check yet.

TIA
Rich Wong

 

[Hass]

Hello Rich,

Sounds like the Main relay. Has your nsx has been sitting for some time? Mine clicked couple of times while jumping the car (had been sitting for several months), started without the click this evening (didn’t need a jump bc I drove it for a few miles in the morning).

-hass

 

[Old Guy]

When does the clicking occur? If its on start up then its likely the Main FI relay and that would be normal. If the clicking occurs while the car is running it is not the main FI relay because you would be getting a hesitation each time the relay opened (cuts power to the ECU or fuel pump). On the later cars there is a speed pulser unit on the back bulkhead. If your noise is speed dependent then check the pulser unit. The pulser unit should not be capable of making any noise; but, some owners have reported a noise associated with the pulser. I can't confirm or refute those claims.

 

[drew]

AT? Every time you let off the brake?

 

[Solidsneak]

AT? Every time you let off the brake?

Ive got this same issue in my 02 as well it just randomly stared one day and it happens at idle or while moving. Have inspected the main relay which was fine no cracks and replaced both 4p relays on the bulkhead just to be safe. The car starts and drives fine but its an annoying sound. There are no codes and no other symptoms just clicking at various RPMs and drive states but nothing else correlates.

I have also seen the pulse unit mentioned but it is entirely solid-state so no clue how it would make any noise or for what reason. I'm deft at a loss as to what it is or could be...

 

[03 raw nsx]

AT? Every time you let off the brake?

No my car is manual. And the brake on/off does not change the clicking

 

[03 raw nsx]

fu

Ive got this same issue in my 02 as well it just randomly stared one day and it happens at idle or while moving. Have inspected the main relay which was fine no cracks and replaced both 4p relays on the bulkhead just to be safe. The car starts and drives fine but its an annoying sound. There are no codes and no other symptoms just clicking at various RPMs and drive states but nothing else correlates.

I have also seen the pulse unit mentioned but it is entirely solid-state so no clue how it would make any noise or for what reason. I'm deft at a loss as to what it is or could be...

I took off the upper bulkhead trim and found out it was the fuel pump relay. I ordered the fuel pump relay, but I have a feeling it will not fix it. I think the problem could be something else. Fuel pump...? Or something causing high resistance. The relay is just too simple or maybe I just don't drive it enough :biggrin:.

 

[Solidsneak]

I took off the upper bulkhead trim and found out it was the fuel pump relay. I ordered the fuel pump relay, but I have a feeling it will not fix it. I think the problem could be something else. Fuel pump...? Or something causing high resistance. The relay is just too simple or maybe I just don't drive it enough :biggrin:.

So I just swapped mine out for new ones and while its slightly quieter its still doing it, but now I've got bigger problems in that my alternator sounds like a SC so I've most likely got a dead diode or a failing bearing. Anecdotally there was another post a few years ago of someone who had this issue as well and it turned out to be their alternator. So hopefully its that if not I'm out of guesses...

 

[03 raw nsx]

There is only a few things connected to that fuel pump relay...
- Fuel Pump resistor
- Main Relay
- ECM
- Fuel Pump

 

[Solidsneak]

There is only a few things connected to that fuel pump relay...
- Fuel Pump resistor
- Main Relay
- ECM
- Fuel Pump

Yea, maybe the fuel pump as the last guess I really dont know, but I've got no stumbles or hesitation nor has it been hard starting or stalling so I doubt its that. Also my car has been stock and NA its entire life so its not like its really lived a hard life per-se' for the pump to die. This would be the first car I've owned where it was stock and the pump died.

 

[Old Guy]

I can't remember whether the fuel pump relay by-passes the fuel pump resistor during the start up sequence; but, it is definitely de-energized during idle and low engine load operation. You definitely should not be hearing the fuel pump relay click on - off if you are just driving around and not entering V Tec mode (high engine load). If you want to confirm that the problem is the fuel pump relay, just remove it. This will leave the fuel pump resistor continuously in the fuel pump circuit (low voltage mode for the pump). You can drive around without any problems as long as you don't go wide open throttle or do anything that would cause the engine to enter V tec mode.

If the noise goes away with the relay removed, then the relay may be the source of the noise. However, I suspect that the relay is not the cause of the problem. As long as the engine is in non V tec mode the relay should stay open (be de-energized) and you should not be hearing it go click - click if you are doing relaxed driving. If the relay is going click - click when you are just driving around in non V tec mode, then you have one of two problems. The ECU is sending erroneous on-off signals to the relay or you have an intermittent short to ground on the red wire between the fuel pump relay and the ECU that is causing the relay to open and close.



The ECU monitors the pump voltage (black/red wire); but, I don't know what control action it takes with that signal. Check to make sure the black/red wire is OK.

 

[03 raw nsx]

You're the best! thanks for the troubleshooting guide.

I can't remember whether the fuel pump relay by-passes the fuel pump resistor during the start up sequence; but, it is definitely de-energized during idle and low engine load operation. You definitely should not be hearing the fuel pump relay click on - off if you are just driving around and not entering V Tec mode (high engine load). If you want to confirm that the problem is the fuel pump relay, just remove it. This will leave the fuel pump resistor continuously in the fuel pump circuit (low voltage mode for the pump). You can drive around without any problems as long as you don't go wide open throttle or do anything that would cause the engine to enter V tec mode.

If the noise goes away with the relay removed, then the relay may be the source of the noise. However, I suspect that the relay is not the cause of the problem. As long as the engine is in non V tec mode the relay should stay open (be de-energized) and you should not be hearing it go click - click if you are doing relaxed driving. If the relay is going click - click when you are just driving around in non V tec mode, then you have one of two problems. The ECU is sending erroneous on-off signals to the relay or you have an intermittent short to ground on the red wire between the fuel pump relay and the ECU that is causing the relay to open and close.

View attachment 169943

The ECU monitors the pump voltage (black/red wire); but, I don't know what control action it takes with that signal. Check to make sure the black/red wire is OK.

 

[Heineken]

Just as a side note: The fuel pump resistor in the engine room is prone to corrosion at the connection pins.
I'm not sure how and if this could feed back to the relay causing it to switch on and off but maybe it's worth having a look.

 

[Solidsneak]

I can't remember whether the fuel pump relay by-passes the fuel pump resistor during the start up sequence; but, it is definitely de-energized during idle and low engine load operation. You definitely should not be hearing the fuel pump relay click on - off if you are just driving around and not entering V Tec mode (high engine load). If you want to confirm that the problem is the fuel pump relay, just remove it. This will leave the fuel pump resistor continuously in the fuel pump circuit (low voltage mode for the pump). You can drive around without any problems as long as you don't go wide open throttle or do anything that would cause the engine to enter V tec mode.

If the noise goes away with the relay removed, then the relay may be the source of the noise. However, I suspect that the relay is not the cause of the problem. As long as the engine is in non V tec mode the relay should stay open (be de-energized) and you should not be hearing it go click - click if you are doing relaxed driving. If the relay is going click - click when you are just driving around in non V tec mode, then you have one of two problems. The ECU is sending erroneous on-off signals to the relay or you have an intermittent short to ground on the red wire between the fuel pump relay and the ECU that is causing the relay to open and close.

View attachment 169943

The ECU monitors the pump voltage (black/red wire); but, I don't know what control action it takes with that signal. Check to make sure the black/red wire is OK.

Yea I tried all of those steps and the relay is brand new and cross checked with a similar one from on the passenger side of the bulkhead. There are no shorts anywhere I can see. The loom is completely untouched.

 

[Solidsneak]

Just as a side note: The fuel pump resistor in the engine room is prone to corrosion at the connection pins.
I'm not sure how and if this could feed back to the relay causing it to switch on and off but maybe it's worth having a look.

This was my next step after the alternator is back from rebuild.

 

[03 raw nsx]

Just as a side note: The fuel pump resistor in the engine room is prone to corrosion at the connection pins.
I'm not sure how and if this could feed back to the relay causing it to switch on and off but maybe it's worth having a look.

That is a really good point :smile:

 

[Old Guy]

Yea I tried all of those steps and the relay is brand new and cross checked with a similar one from on the passenger side of the bulkhead. There are no shorts anywhere I can see. The loom is completely untouched.

"I tried all of those steps"

As in 'you removed the fuel pump relay and the clicking stopped', in which case the noise is related to the fuel pump relay or 'you removed the fuel pump relay and the clicking was still present' in which case the noise is unrelated to the fuel pump relay?

 

[Solidsneak]

"I tried all of those steps"

As in 'you removed the fuel pump relay and the clicking stopped', in which case the noise is related to the fuel pump relay or 'you removed the fuel pump relay and the clicking was still present' in which case the noise is unrelated to the fuel pump relay?

Pulled the relay clicking stopped which lead me to believe it was a bad or dying relay but I have since(1 day ago) replaced it and its mate on the passenger side with brand new Denso relays and the clicking is back on the drivers side. Have held my hand on it while driving and confirmed it was the one clicking.

Strangely this maybe entirely anecdotal the clicking will stop if the AC is off with the relay plugged in but turn the AC on and the clicking returns.

Lastly with the relay plugged in and stationary raise the RPM to 2000 and clicking commences lower them and it stops...

 

[Old Guy]

Pulled the relay clicking stopped which lead me to believe it was a bad or dying relay but I have since(1 day ago) replaced it and its mate on the passenger side with brand new Denso relays and the clicking is back on the drivers side. Have held my hand on it while driving and confirmed it was the one clicking.

Strangely this maybe entirely anecdotal the clicking will stop if the AC is off with the relay plugged in but turn the AC on and the clicking returns.

Lastly with the relay plugged in and stationary raise the RPM to 2000 and clicking commences lower them and it stops...

That is definitely strange behavior. That relay should not be operating at low engine outputs. If you confirmed that you don't have some sort of intermittent ground on the red wire between the fuel pump relay and the ECU, then the ECU must be applying errant grounds causing the relay to operate (the ECU connects the red wire to ground to operate the relay). The ECU uses an internal transistor to switch the relay on and off; but when transistors fail they usually stay failed and most commonly as an open circuit. It might be possible that the ECU is getting some erroneous input signals causing the relay to engage and disengage.

The explanation of the fuel pump control in the service manual is minimal. It is not clear what that sense wire from the output of the fuel pump relay back to the ECU does. Perhaps [MENTION=18194]Honcho[/MENTION] or [MENTION=33247]MotorMouth93[/MENTION] can advise on the fuel pump control features in the ECU if they have come across it during the characterization of the ECU firmware.

 

[Solidsneak]

Problem Solved!!

So I have solved the problem, apparently it was the alternator which was causing the issue. I just reinstalled my rebuilt alternator and no more clicking!!!! I have no clue as why or what the actual cause was but I'll take it!! So if you have clicking of the fuel resistor and your relays are good check your alternator it maybe dying and not long for the world.

FYI: My alternator had a bad diode next to the regulator and worn bushes in addition to failing bearings.

 

[03 raw nsx]

So I have solved the problem, apparently it was the alternator which was causing the issue. I just reinstalled my rebuilt alternator and no more clicking!!!! I have no clue as why or what the actual cause was but I'll take it!! So if you have clicking of the fuel resistor and your relays are good check your alternator it maybe dying and not long for the world.

FYI: My alternator had a bad diode next to the regulator and worn bushes in addition to failing bearings.

Nice!! I have a spare alternator if that is the cause, but I don't suspect it. In my case because the car only has 23k miles.

 

[Solidsneak]

Nice!! I have a spare alternator if that is the cause, but I don't suspect it. In my case because the car only has 23k miles.

Alternators don't necessarily fail due to mileage they die from heat and age more than anything, mileage is typically an accompanying symptom or trigger for lack of better wording. Id def swap it to verify though esp if you have a known good spare.

 

[acuhon]

Nice!! I have a spare alternator if that is the cause, but I don't suspect it. In my case because the car only has 23k miles.

Did swaping altenator helped? My 97 with 210K miles started to play morse code. Got to get it ready for NSXPO.

 

[03 raw nsx]

Sorry, I been offline.
No, it did not help. But changing the ground cable from my battery to the frame and cleaning the battery terminals helped.
Have fun at NSXPO!

 

[acuhon]

Sorry, I been offline.
No, it did not help. But changing the ground cable from my battery to the frame and cleaning the battery terminals helped.
Have fun at NSXPO!

Replacing ignition switch fixed my clicking problem. Thanks Richard. I hope that some guys from SF will make it to NSXPO. That drive from SF to LA was epic.
Just installed new Rivals and Hawk + . Almost ready.